The issue with the battery will depend on the way that the reader is charged, for example, these Sony readers are drained out if you leave it charging for too long, charging overnight or more than 5 o 6 hours will drain the power that it already had.
Just make sure to reset the reader before charging it,(just push the reset hole and it will not delete anything) then get it to charge for no more than 3 o 4 hours and see if that helps or the behavior comes back
